JP-A 10-273494 discloses that a phosphite represented by the formula (1):
wherein R1, R2, R4 and R5 independently represent a hydrogen atom, an alkyl group of 1 to 8 carbon atoms, a cycloalkyl group of 5 to 8 carbon atoms, an alkylcycloalkyl group of 6 to 12 carbon atoms, an aralkyl group of 7 to 12 carbon atoms or a phenyl group,
R3 represents a hydrogen atom or an alkyl group of 1 to 8 carbon atoms,
X presents a single bond, a sulfur atom or a —CHR6— group, in which R6 presents a hydrogen atom, an alkyl group of 1 to 8 carbon atoms or a cycloalkyl group of 5 to 8 carbon atoms,
A represents an alkylene group of 2 to 8 carbon atoms or a *—COR7— group, in which R7 represents a single bond or an alkylene group of 1 to 8 carbon atoms, and the symbol * represents a point being linked with the oxygen atom of the >P—O— group in the formula (1),
one of Y and Z represents a hydroxyl group, an alkoxy group of 1 to 8 carbon atoms or an aralkyloxy group of 7 to 12 carbon atoms, and the other represents a hydrogen atom or an alkyl group of 1 to 8 carbon atoms,
when Y is a hydroxyl group, one of R4 and R5 represents an alkyl group of 3 to 8 carbon atoms, a cycloalkyl group of 5 to 8 carbon atoms, an alkylcycloalkyl group of 6 to 12 carbon atoms, an aralkyl group of 7 to 12 carbon atoms or a phenyl group, and
R1, R2 and R3 may be the same or different, is for use as an agent for preventing deterioration of a thermoplastic resin such as polyolefin. Specifically, JP-A 10-273494 discloses that a resin composition in a pellet form is obtained by melt-kneading polypropylene together with calcium stearate, which is a metal soap, and a phosphite as additives, and said resin composition slightly undergoes coloring caused by exposure to an NOx gas, that is, has good coloring resistance.
However, the phosphite described in JP-A 10-273494 is usually in a powder form having an average particle diameter of around 20 to 60 μm, so that there is a problem that dust is raised when the phosphite is added to a thermoplastic resin.
For solving such a problem of dust raised upon addition of an additive composition comprising a phosphite and a metal soap, JP-A 2001-81236 discloses that a metal soap and further an organic compound having a lower melting point than that of a metal soap (specifically, glycerin monostearate) as a binder is added to a phosphate metal salt, instead of a phosphite ester, as a main component to obtain a granular additive composition, and said granular additive composition hardly produces dust. In addition, JP-A 2001-81236 discloses that an additive composition containing a lubricant (e.g. polypropylene wax having a molecular weight of 7000 and a melting point of 140° C.) as a binder is hardly dispersed in a thermoplastic resin.